This invention relates to a fluid drive vehicle and more particularly to a fluid actuated control system which provides simultanoeus and coordinated control of engine speed, transmission drive ratio and direction of travel with a single control and an override device for control of the transmission drive ratio without affecting engine speed.
Many forms of industrial and earthmoving vehicles are often provided with hydrostatic transmissions for coupling the engine to the drive shaft or other running gear of the vehicle. On some of those vehicles, particularly lift trucks and loaders, it is desirable to be able to simultaneously control the engine speed, vehicle speed and direction of travel with a single pedal to free the operator's hands for controlling other vehicular controls. It is also desirable to have an override control to reduce the vehicle speed without affecting the position of the single pedal and/or engine speed. Heretofore, the pedal has been connected to the transmission controls and engine speed controls through a mechanical linkage. However, one disadvantage of such mechanical linkages is that they are difficult to install, adjust and service, and the forces required to actuate the pedal are relatively high thereby contributing greatly to operator fatique. Also, with such linkages, a different linkage arrangement is generally required for every vehicle model. This requires an inventory of a greater number of parts to provide for servicing and replacement of worn and broken parts.